Meant for room sizes of 280 sq. ft., the unique feature in the 'i' models is the presence of an air quality sensor that speeds up the fans automatically whenever it detects a drop in the air quality of the room. Apart from that, the Classic 280i purifies the air using their patented HEPASilent technology. It has a smart panel on top to display Wi-Fi connectivity, fan speed status, filter status and the air quality of the room including PM 2.5 and VOC levels. The Blueair Friend app will let you control all the modes remotely without touching the purifier but it needs some work. You can also monitor the air quality of your room in real-time and accordingly set the fan speed.